Gao Y, Vanhoutte P M
Department of Physiology and Biophysics, Mayo Clinic, Rochester, Minnesota.
Lung. 1992;170(6):339-47. doi: 10.1007/BF00177580.
The present study was designed to investigate the effect of changes in osmolarity on the modulatory role of the respiratory epithelium on the underlying smooth muscle. Canine bronchial segments with or without epithelium were perfused intraluminally with modified Krebs-Ringer bicarbonate solution. The transluminal isometric tension was recorded by means of stirrups passed through the bronchial wall. During contractions to extraluminal carbachol, the tissues with epithelium exhibited epithelium-dependent relaxations to hypotonic solution given intraluminally. The level of relaxation was dependent on the osmotic pressure. No significant difference was noted between relaxations due to hypotonic solution made by mixing the Krebs-Ringer solution with distilled water and those made by decreasing the concentration of sodium chloride. The epithelium-dependent relaxations could not be blocked by the antagonists or blockers of cyclo-oxygenase, endothelium-derived relaxing factor, alpha-adrenoceptors, beta-adrenoceptors, and sodium channels. No evidence for the release of a relaxing factor into the bronchial lumen was found in bioassay study. When the preparation was stimulated with hypertonic solutions prepared by adding mannitol or urea, similar relaxations were induced in tissues with and without epithelium. These observations suggest that changes in osmolarity affect the responses of canine bronchi to carbachol and that the epithelium modulates the responses of airway to hypotonic solutions.
本研究旨在探讨渗透压变化对呼吸道上皮对其下方平滑肌的调节作用的影响。对有或无上皮的犬支气管段进行腔内灌注改良的 Krebs-Ringer 碳酸氢盐溶液。通过穿过支气管壁的马镫记录跨腔等长张力。在对腔外卡巴胆碱的收缩过程中，有上皮的组织对腔内给予的低渗溶液表现出依赖上皮的舒张。舒张程度取决于渗透压。将 Krebs-Ringer 溶液与蒸馏水混合制成的低渗溶液引起的舒张与降低氯化钠浓度制成的低渗溶液引起的舒张之间无显著差异。依赖上皮的舒张不能被环氧化酶、内皮源性舒张因子、α-肾上腺素能受体、β-肾上腺素能受体和钠通道的拮抗剂或阻滞剂阻断。生物测定研究未发现有舒张因子释放到支气管腔内的证据。当用添加甘露醇或尿素制备的高渗溶液刺激标本时，有上皮和无上皮的组织均诱导出类似的舒张。这些观察结果表明，渗透压变化影响犬支气管对卡巴胆碱的反应，并且上皮调节气道对低渗溶液的反应。
